The proposed research activities include a series of experiments on the role of excitatory amino acids on psychomotor stimulant sensitization. One objective will be to study the interesting contrast between systemic injections of amphetamine which show sensitization and intracranial injections of amphetamine (into the nucleus accumbens) which does not. Excitatory amino acids have been proposed to be involved in the sensitization. The overall purpose is to understand how excitatory amino acids participate in the mechanisms involved in psychomotor stimulant sensitization.